Simplify the following expression: $z = \dfrac{n}{4} - \dfrac{5n}{6}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $4$ and $6$ $\lcm(4, 6) = 12$ $ z = \dfrac{3}{3} \cdot \dfrac{n}{4} - \dfrac{2}{2} \cdot \dfrac{5n}{6} $ $z = \dfrac{3n}{12} - \dfrac{10n}{12}$ $z = \dfrac{3n -10n}{12}$ $z = \dfrac{-7n}{12}$